Date: Mon, 9 Feb 2009 09:23:45 -0500 From: John Baldwin <jhb@freebsd.org> To: Marcel Moolenaar <xcllnt@mac.com> Cc: svn-src-head@freebsd.org, Scott Long <scottl@samsco.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, "M. Warner Losh" <imp@bsdimp.com> Subject: Re: svn commit: r188350 - in head/sys: amd64/amd64 arm/arm dev/usb2/core i386/i386 ia64/ia64 sys Message-ID: <200902090923.45887.jhb@freebsd.org> In-Reply-To: <94616FBD-4638-4C51-990C-06A943B1BA2A@mac.com> References: <200902082254.n18MsxVt037307@svn.freebsd.org> <498F8015.8000704@samsco.org> <94616FBD-4638-4C51-990C-06A943B1BA2A@mac.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Monday 09 February 2009 12:37:53 am Marcel Moolenaar wrote: > > On Feb 8, 2009, at 5:00 PM, Scott Long wrote: > > > Busdma allows you to request bouncing for realignment. > > How exactly? The 'align' parameter to bus_dma_tag_create(). If your hardware needs buffers to be aligned on a 4-byte boundary and you bus_dmamap_load() a buffer where 'addr % 4 != 0', then the buffer is bounced. Since by default the new buffer starts on a page boundary, it satifies the 'addr % 4'. -- John Baldwin
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200902090923.45887.jhb>